SetPartitioner (using gevent) fails when lock acquisition is aborted

[emulbreh]

SetPartitioner._abort_lock_acquisition() doesn't pass async=True to _child_watching(), which causes the rawlinked function (_allocate_transition()) to be executed directly from the event loop callback:

Traceback (most recent call last):
  File "/.../env/src/gevent/gevent/event.py", line 293, in _notify_links
    link(self)
  File "/.../env/lib/python2.7/site-packages/kazoo/recipe/partitioner.py", line 273, in _allocate_transition
    self._identifier, list(self._party), self._set)
  File "/.../env/lib/python2.7/site-packages/kazoo/recipe/party.py", line 63, in __len__
    return len(self._get_children())
  File "/.../env/lib/python2.7/site-packages/kazoo/recipe/party.py", line 66, in _get_children
    return self.client.retry(self.client.get_children, self.path)
  File "/.../env/lib/python2.7/site-packages/kazoo/retry.py", line 122, in __call__
    return func(*args, **kwargs)
  File "/.../env/lib/python2.7/site-packages/kazoo/client.py", line 945, in get_children
    return self.get_children_async(path, watch, include_data).get()
  File "/.../env/src/gevent/gevent/event.py", line 233, in get
    result = self.hub.switch()
  File "/.../env/src/gevent/gevent/hub.py", line 344, in switch
    switch_out()
  File "/.../env/src/gevent/gevent/hub.py", line 348, in switch_out
    raise AssertionError('Impossible to call blocking function in the event loop callback')
AssertionError: Impossible to call blocking function in the event loop callback
(<bound method SetPartitioner._allocate_transition of <kazoo.recipe.partitioner.SetPartitioner object at 0x10a74a9d0>>,
 <gevent.event.AsyncResult object at 0x10a92a250>) failed with AssertionError

#240 is my attempt to fix this problem. Maybe it would be cleaner to default to async=True or even remove the parameter.

[timcherry]

Running into the same issue.

In cases where we don't set async=True we need to be extra careful not to use blocking calls in the callback, as gevent calls rawlink callbacks from inside the hub greenlet.

The workaround, as stated by @emulbreh, is to set async=True. It may be a better long term solution to use a Condition() here similar to the SequentialThreadingHandler.

[ninowalker]

👍 Seeing this as well.

[StephenSorriaux]

Closing this issue since it was fixed with #283. Thank you.